Purification and Characterization of a Versatile Peroxidase from Edible Mushroom Pleurotus eryngii

Bioremoval and Detoxification of the Anticancer Drug Mitoxantrone Using Immobilized Crude Versatile Peroxidase (icVP/Ba) Bjerkandera adusta CCBAS 930

The aim of this study was to evaluate the biodecolorization and detoxification of the anticancer drug mitoxantron (MTX) by immobilized crude versatile peroxidase of Bjerkandera adusta CCBAS 930 (icVP/Ba). The concentrated crude VP was obtained from B. adusta CCBAS 930 culture on medium with MTX (µg/mL) addition, immobilized with 4% sodium alginate. MTX removal degree (decolorization), levels of phenolic compounds and free radicals were determined during MTX biotransformation. Moreover, the phytotoxicity (Lepidium sativum L.), biotoxicity (multi-species microbial assay, MARA), and genotoxicity (SOS Chromotest) of MTX were evaluated before and after the biological treatment. The use of icVP/Ba (95 U/mL) significantly shortened the bioremoval of 10 µg/mL MTX (95.57% after 72 h). MTX removal by icVP/Ba was correlated with an 85% and 90% decrease in the levels of phenolic compounds and free radicals, respectively. In addition, the use of icVP/Ba contributed to a decrease in the phyto-, bio-, and genotoxicity of MTX. This is the first study to describe the possibility of removing MTX using immobilized crude fungal peroxidase.

Cultivation of Mushrooms and Their Lignocellulolytic Enzyme Production Through the Utilization of Agro-Industrial Waste

A large amount of agro-industrial waste is produced worldwide in various agricultural sectors and by different food industries. The disposal and burning of this waste have created major global environmental problems. Agro-industrial waste mainly consists of cellulose, hemicellulose and lignin, all of which are collectively defined as lignocellulosic materials. This waste can serve as a suitable substrate in the solid-state fermentation process involving mushrooms. Mushrooms degrade lignocellulosic substrates through lignocellulosic enzyme production and utilize the degraded products to produce their fruiting bodies. Therefore, mushroom cultivation can be considered a prominent biotechnological process for the reduction and valorization of agro-industrial waste. Such waste is generated as a result of the eco-friendly conversion of low-value by-products into new resources that can be used to produce value-added products. Here, we have produced a brief review of the current findings through an overview of recently published literature. This overview has focused on the use of agro-industrial waste as a growth substrate for mushroom cultivation and lignocellulolytic enzyme production.

A novel and efficient fungal delignification strategy based on versatile peroxidase for lignocellulose bioconversion

BACKGROUND

The selective lignin-degrading white-rot fungi are regarded to be the best lignin degraders and have been widely used for reducing the saccharification recalcitrance of lignocellulose. However, the biological delignification and conversion of lignocellulose in biorefinery is still limited. It is necessary to develop novel and more efficient bio-delignification systems.

RESULTS

Physisporinus vitreus relies on a new versatile peroxidase (VP)-based delignification strategy to remove enzymatic recalcitrance of corn stover efficiently, so that saccharification of corn stover was significantly enhanced to 349.1 mg/g biomass (yield of glucose) and 91.5% (hydrolysis yield of cellulose) at 28 days, as high as levels reached by thermochemical treatment. Analysis of the lignin structure using pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) showed that the total abundance of lignin-derived compounds decreased by 54.0% and revealed a notable demethylation during lignin degradation by P. vitreus. Monomeric and dimeric lignin model compounds were used to confirm the ligninolytic capabilities of extracellular ligninases secreted by P. vitreus. The laccase (Lac) from P. vitreus could not oxidize nonphenolic lignin compounds and polymerized β-O-4 and 5-5' dimers to precipitate which had a negative effect on the enzymatic hydrolysis of corn stover in vitro. However, the VP from P. vitreus could oxidize both phenolic and nonphenolic lignin model compounds as well as break the β-O-4 and 5-5' dimers into monomeric compounds, which were measured by high-performance liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS). Moreover, we showed that addition of purified VP in vitro improved the enzymatic hydrolysis of corn stover by 14.1%.

CONCLUSIONS

From the highly efficient system of enzymatic recalcitrance removal by new white-rot fungus, we identified a new delignification strategy based on VP which could oxidize both phenolic and nonphenolic lignin units and break different linkages in lignin. In addition, this is the first evidence that VP could break 5-5' linkage efficiently in vitro. Moreover, VP improved the enzymatic hydrolysis of corn stover in vitro. The remarkable lignin-degradative potential makes VP attractive for biotechnological applications.